1. Field of the Invention
The present invention relates to a disc drive for playing back or recording and playing back a disc such as an optical disc, and in particular relates to a disc drive equipped with a device for reading a bar code provided on an optical disc.
2. Description of the Prior Art
FIG. 1 is an exploded perspective view which shows the structure of one example of conventional disc drives for playing back or recording and playing back an optical disc 3.
As shown in FIG. 1, a disc drive 1C is roughly constructed from a main body 2 and a disc tray 5 which moves backwards and forwards in the horizontal direction with respect to the main body 2.
The main body 2 is roughly constructed from a bottom plate 11, a main circuit substrate assembly 12 arranged on the bottom plate 11, a mechanism assembly 13 provided on the main circuit substrate assembly 12 and a casing 14 which covers the mechanism assembly 13.
The casing 14 is provided with a top plate portion 14a. On the underside surface (inner surface) of the top plate portion 14a, a disc clamper 38 is rotatably mounted such that its rotational axis is aligned with that of a turntable 26 described below. The casing 14 is attached to the upper portion of the mechanism assembly 13 by means of screws 17, and the bottom plate 11 is attached to the lower portion of the mechanism assembly 13 by means of screws 17 with the main circuit substrate assembly 12 being interposed therebetween.
Formed in the front plate 14e of the case 14 is an aperture 14f through which the disc tray 5 is passed. A front panel 15 having an aperture 15a corresponding to the aperture 14f is mounted to the front plate 14e via a cushioning frame member 15 formed from a sponge.
The mechanism assembly 13 includes a roughly container-shaped chassis 20 which is provided with a mechanism unit 22 and a loading mechanism 30. The mechanism unit 22 is arranged within a concave portion formed in the bottom portion 20a of the chassis 20, and the loading mechanism 30 is arranged in front of the concave portion 21 of the chassis 20.
The mechanism unit 22 includes a base 23 which is provided with a spindle motor 25 for rotating an optical disc 3, a turntable 26 which is fixed to a rotation axis of the spindle motor 25, an optical pick-up (optical head) 27, an optical pick-up moving mechanism 28 and a photo-interrupter for reading a bar code of the optical disk 3. Further, a rear end portion (on the back side of the main body 2) of the base 23 is supported by an insulator 29 to enable the base 23 to be freely pivotal with respect to the chassis 20.
The loading mechanism 30 is constructed from a loading motor 31 provided at one side of the front portion of the chassis 20, a rotational speed reduction mechanism 32 for transmitting the rotation of the loading motor 31 with a reduced rotational speed, a cam wheel (ascending/descending gear) 33 which is rotated via the rotational speed reduction mechanism 32, and a base ascending/descending member (not shown in the drawing) which is displaced (pivoted) in accordance with the rotation of the cam wheel 33.
The cam wheel 33 includes a lower gear 33a which meshes with a pinion gear of the rotational speed reduction mechanism 32, and an upper gear 33b which meshes with a rack gear (not shown in the drawing) formed on the back surface of the disc tray 5 along the longitudinal direction (in the forward and backward direction) thereof. Further, a circumferential cam groove is formed in the outer circumference of the axle portion between the gears 33a and 33b. This cam groove receives a protruding follower (not shown in the drawing) formed on the base ascending/descending member. Consequently, as the cam wheel is rotated, the follower and the base ascending/descending member are displaced, and this causes the base 23 to pivot; namely, the front portion of the base 23 is pivotally moved up or down between an ascending position (raised position) and a descending position (lowered position).
Further, as stated in the above, the disc clamper 38 is provided on the top plate 14a of the casing 10 in such a manner that the disc clamper 38 is rotatable with respect to the top plate 14. The disc clamper 38 is adapted to attach to the permanent magnet provided in the turntable 26 by the attracting force thereof, whereby the optical disc 3 can be held between the turntable 26 and the disc clamper 38.
The disc tray 5 includes a shallow concave disc supporting portion 5a for supporting the optical disc 3, and as described above the rack gear is formed on the back surface thereof (not shown in the drawing) which meshes with the upper gear 33b of the cam wheel 33. Consequently, as the cam wheel 33 is rotated, the disk tray 5 is moved forward or backward with respect to the chassis 20 between a disc loaded position (playback position) and a disc placing/removing position (eject position).
When the disc drive 1C is not in use, the disc tray 5 is housed within the casing 10 (at the disk loaded position/playback position). In this state, if an eject operation is carried out, the motor 31 is rotated in a prescribed direction, whereby the cam wheel 33 is rotated in a counterclockwise direction via the rotational speed reduction mechanism 32. This rotation of the cam wheel 33 causes the disc tray 5 to move forward (toward the front side of the disc drive) to the disc eject position protruded outside the casing 10 through the apertures 14f, 15a.
In this state, an optical disc 3 is placed on the disc supporting portion 5a of the disc tray 5, and a loading operation is then carried out, whereby the motor 31 is rotated in the opposite direction, and this causes the cam wheel 33 to rotate in the opposite direction via the rotational speed reduction mechanism 32. Consequently, the disc tray 5 is moved toward the rear of the disc drive, through the apertures 14f, 15a, to the disc loaded position. In this way, the optical disc 3 which is placed at a prescribed position on the disc tray 5 is also transported to the disc loaded position of the main body 2.
Then, the center portion (center hub portion) of the turntable 26 is fitted into a center hole 3a of the optical disc 3, and as the center portion of the optical disc is supported in this way, the disc clamper 38 is magnetically stuck to the turntable 26, with the optical disc 3 being held between the turntable 26 and the disc clamper 38. In this state, the spindle motor 25 is operated to rotate the optical disc 3 at a predetermined rotational speed, and then the information recorded on the optical disc 3 is played back or reproduced using the optical pick-up 27.
If an eject operation is carried out while the rotation of the optical disc 3 is stopped, the operations of each mechanism of the disc drive 1C described above are carried out in reverse order and direction, thereby the disc clamper 38 is released and then the optical disc 3 supported on the disc tray 5 is ejected.
In the meantime, there are optical discs which are provided with an identification indication such as a bar code or the like to specify various information. For example, in the case of an optical disc 3 such as a photo CD developed by Kodak, Inc., as shown in FIG. 2, an arc-shaped bar code 3d is provided on an annular bar code area 3c formed between a clamping area 3b and a program area 3e of the optical disc 3. With this bar code 3d, it is possible to specify various information such as the disc manufacturer and the date of manufacturing, thereby enabling to determine the type of disc, the disc format and the like. In order to read the bar code of an optical disc such as the photo CD, a photo-interrupter for reading bar code information must be provided in addition to an optical pick-up for reading data recorded in the program area 3e of the optical disc.
In this connection, FIG. 3 shows an example of a disc drive which includes such a photo-interrupter (Japanese Laid-Open Patent Application HEI 7-182659). As shown in this drawing, in this disc drive a photo-interrupter 9a is mounted on a sensor platform 9 which is provided in the vicinity of a turntable 8. Thus, by means of the photo-interrupter 9a, the bar code of the loaded optical disc is read from the lower side of the optical disc.
In this way, in the disc drives of the prior art, the photo-interrupter 9a is positioned underneath the optical disc, namely, the photo-interrupter 9a is positioned at the side where the optical pick-up and the turntable 8 are provided, and thereby the bar code is read from underneath the loaded optical disc.
However, before optical discs having the bar code such as photo CDs became widespread, disc drives were not equipped with a photo-interrupter, and for this reason the design of such disc drives did not take into consideration the provision of a photo-interrupter mounting space in the periphery of the turntable. As a result, in order to make it possible to reproduce bar coded optical discs such as photo CDs, a photo-interrupter mounting space must be provided in the disc drive.
In this regard, a position where the photo-interrupter is to be mounted is determined by the fixed positional relationship between the mounting position of the photo-interrupter and the bar code affixed to the optical disc. However, around such a position, various components such as a spindle motor and an optical pick-up moving mechanism have been already provided, so that this greatly limits the places where the photo-interrupter can be mounted. Consequently, there is very little freedom of design, and therefore this makes it difficult to manufacture disc drives adapted to photo CDs and the like based on the design of existing disc drives.